public class StuDemo{
    public static void main(String[] args) {
//        test2();
//        test3();
          test4();
    }
    public static void test1() {

    }
    public  static void test2() {
        String s="name=zhangsan age=18 No=90728";
        for ( String i: s.split(" ")) {
            System.out.println(i);
        }

    }
    public  static void test2_0() {
        String s="name=zhangsan age=18 No=90728";
        char[] chars= s.toCharArray();
        for (int i = 0; i <0; i++) {

        }

    }
    public  static  void test3 () {
        StringBuilder s=new StringBuilder("abcd");
        System.out.println(s.reverse());
    }
    public  static  void test4 () {
        String s="abcd";
        char [] sChar=s.toCharArray();
        for (int i = sChar.length-1; i >=0 ; i--) {
            System.out.print(sChar[i]);
        }
    }
}
